Method of manufacturing sealing rings

ABSTRACT

A method of manufacturing sealing rings or the like is disclosed in which the U-shaped cross-section is formed by two successive cold rolling steps. Thinning of the rings at the points of curvature is eliminated by forcing metal to cold flow from the flanges downward into the curved portion of the sealing ring.

United States Patent Qraik Sept. 11, 1973 [54] METHOD OF MANUFACTURINGSEALING 2,697,865 12/1954 Norton 29/156.6 X

RINGS 3,364,550 l/l968 Jessee et al. v 3,381,353 5/1968 Lemmerz IInventor: Dflrrjel Craik, Escondido. Cahf- 3,586,544 6/l97l Geffroy29/l56.6 x [73'] Assignee: 'leledyne, Inc., Los Angeles, Calif. y

. Primary ExaminerRichard J. Herbst I22] 1972 Assistant Examiner-V. A.DiPalma |2ll Appl. No.: 241,977 Attorney-Ronald W. Reagin et al.

[52] US. Cl 29/557, 29/l56.6, 29/l59.l, [57] ABSTRACT 29/159 R, 72/105,1l3/ll6R 51 1m. 01 823p 13/04 A method mahufacmrmg Sea'mg the hke [58]Field of Search 29/557 156.6 159.1 disclhsed which the U'ShaPed (ms-Swimis 29/159 72/105 115/116 formed by two successive cold rolling steps.Thinning of the rings at the points of curvature is eliminated by I 56]Refernces Cited forcing metal to cold flow from the flanges downwardUNITED STATES PATENTS into the curved portion of the sealing ring.

2,227,746 1/1941 Clark 72/106 5 Claims, 6 Drawing Figures FORM TUBULAR26/ RING FIRST COLD 28/ ROLL SECOND COLD J ROLL I l 42 EXPAND RING 44 5HEAT TREAT -l6 EXPAND RING MACHINE 48 AS REQUIRED PATENTEDSEH 1 ma SHEEI1 [if 2 PATENTED'SEPI 1 I973 I SHEET 2 0F 2 Fig.4

Fig. 3

f /IA No Q This invention relates to sealing rings or the like, and moreparticularly to an improved method for manufacturing such rings in whichthe desired cross-section of the ring is formed by cold-rollingtechniques.

It is a common practice to provide a sealing ring at the joint of twopipes or conducts which has a generally U-shaped, inwardly openingcross-section. Such sealing rings are frequently used to seal the jointsbetween pipes which are carrying hot gases under pressure. By theirnature, these sealing rings must be formed to very precise dimensionsand with very small tolerances. Because of these severe dimensionalrequirements, the usual way for manufacturing such sealing rings in theprior art has been to machine them on a lathe from the desired materialinto the desired shape and configuration.

In addition to the obvious economic disadvantages from forming thesealing rings in this manner, there is also a significant performancedisadvantage. Such sealing rings must, by their nature, have goodresilience and elasticity. It is well known that these characteristicsare very much a function of the grain orientation of the metal whichforms the sealing ring. If the ring is machined from a single piece ofmetal which has a constant grain structure and orientation, it isobvious that, at different points around the circumference of the ring,the grain structure is significantly different relative to thecross-sectionalarea of the ring at that point on the circumference.

Those skilled in the art have long recognized that the above mentionedeconomic and performance factors could both be significantly improved ifthe sealing rings could be manufactured by suitable cold rollingtechnique. Such techniques are inherently much cheaper than machiningand alsoresult in a ring which hasa constant grain orientation relativeto the cross-section of the ring all around the circumference of thering.

However, all prior attempts to form such sealing rings by cold-rollingtechniques have been unsuccessful. These prior art attempts have usuallyfailed because the sealing rings could not be formed to the necessaryclose tolerances and because the conventional cold-rolling techniquesinherently resulted in a thinning of the metalat the points of curvatureof the metal. Such thinning is particularly unacceptable in sealingrings of this type because it results in a mechanical weakness of thering at'the point where maximum strength and resilience of the ring isrequired. Thus, it has been widely believed in the prior art thatcold-rolling techniques could not be used to manufacture such sealingrings.

curvature and flanges of a predetermined flange length is provided inwhich the sealing ring is formed from a strip or sheet of metal having adesired initial thickness. In accordance with the method, a tubular bandof metal is first formed from the strip whose diameter is between theabove mentioned predetermined outside and inside diameters of thesealing ring to be formed. Next, this tubular band is cold-rolled in afirst die into a intermediate ring until it has a generally U-shapedinwardly cross-section whose internal radius of curvature is greaterthan the predetermined internal radius of curvature which the final ringis to have and whose flanges are longer than the flanges which are to beformed on the final ring. This intermediate ring is then rolled in asecond die until it has the desired predetermined internal radius ofcurvature. The second die is shaped to engage the inner surface, theouter surface and the ends of the flanges of the ring. Thus, during thesecond rolling operation, the die, by engaging the ends of the flangesof the ring, forces the metal to cold flow from the flanges down intothe curved portion of the crosssection to provide the desired constantthickness of the ring at this point and to prevent thinning of themetals at the curved portion of the ring.

For a complete understanding of the invention, and an appreciation ofits other objects and advantages, please refer to the following detaileddescription of the attached drawings, in which:

FIG. 1 is a plan view of the sealing ring which can be manufactured inaccordance with the method of present inventions;

FIG. 2 is a sectional view taken along the lines 22 of FIG. 1;

FIG. 3 is a block flow diagram of the method in accordance with thepresent invention by which the sealing ring of FIGS. land 2 can bemanufactured;

In accordance with the present invention, it has been discovered that,if the proper steps are taken in the cold-rolling procedure, thesetechniques can be used to form satisfactory sealing rings of the typementioned above which have the necessary accurate dimensions and closetolerances.

It is accordingly the object of the present invention FIG. 4 is across-sectional view of the first and second rolling dies used with thepresent invention;

FIG. 5 is a cross-sectional view of the sealing ring after it has passedthrough the first die of FIG. 4; and

FIG. 6 is a cross-sectional view of the sealing ring after it has passed.through the second die of FIG. 4.

FIG. 1 is a plan view of a sealing ring which can conveniently bemanufactured by the method of the present invention and FIG. 2 is across-sectional view of the sealing ring taken along the line 22 inFIG. 1. For

convenience, the following description is of FIGS. l

and 2 simultaneously.

, The sealing ring 10 is a circular ring which has a generally U-shapedinwardly opening cross-section which includes a curved outer portion 12and two flanges l4 and 16. Each of the flanges I4 and 16 terminates withan end surface 18 and 20 respectfully. In a typical sealing ring 10, thethickness of the flanges 14 and 16 gradually decreases in the directionaway from the curved section 12 of the ring 10. This is done to providethe desired resilient properties in the flanges 14 and 16. Also, in mostsuch sealing rings 10, land portions 22 and 24 are provided near theends of flanges l4 and-l6 respectively.

While the present invention is not limited to forming sealing ringshaving any particular size or dimensions,

thickness of the walls of the sealing ring in the curved section 12 is0.040 inches. The length of the flanges 14 and 16 is such that thedimension L is 0.200 inches. The internal radius of curvature R of thegenerally U- shaped cross-section is 0.025 inches. These dimensions aregiven merely to assist in the description of the invention in themanufacture of a typical sealing ring 10. Those skilled in the art willreadily appreciate how to use the method of the invention to formsealing rings having other desired dimensions.

FIG. 3 shows a block flow diagram of the steps of the present inventionby which the sealing ring 10 shown in FIGS. 1 and 2 can easily andeconomically be formed to precise dimensions. As is shown in FIG. 3, thefirst step 26 is to form a tubular ring of the proper thickness andwidth and whose diameter is between the inside and outside diameter ofthe ring 10 to be formed. Preferably this is formed from a sheet metalblank or strip formed from the desired material of proper thickness,width and length. To form the ring having the dimensions describedabove, such a strip of nickel base alloy is formed which has a thicknessof 0.040 inches, a width of 0.450 inches and a length of 10.985 inches.The strip is then coiled into a tubular ring, and the ends of thetubular ring are held in a suitable clamping device and welded together.Thereafter, the weld is properly dressed as desired. The manner offorming such a tubular ring is well known to those skilled in the art,so no further details are given herein.

Alternatively, instead of forming one tubular ring at a time in themanner described above, an entire sheet of metal could be formed into along tube, and tubular rings of the proper width could be sliced fromthe long tube in any desired manner.

The next step 28 in the method is to pass the tubular ring as formed inthe step 26 through a first cold-rolling die. FIG. 4 shows across-sectional view of two such cold-rolling dies, one of which is afirst cold rolling die 30 which includes a male rolling member 32 and afemale rolling member 34.

As is shown in FIG. 4, the elements of the first rolling die 30 areformed such that, when the male member 32 is withdrawn from the femalemember 34, a shelf 36 exists in the female member 34 which receives thetubular ring formed in the step 26 above. When the ring is placed on theshelf 36 and the two portions of the first rolling die 30 are broughttogether in a rolling relation, the dimensions of the male member 32 andthe female member 34 are such that the tubular ring is cold-rolled intothe space 38 which has a generally U-shaped, inwardly openingcross-section.

FIG. shows the cross-section of the ring after it has been passedthrough the first rolling die 30. As is shown in FIG. 5, thecross-section is now a generally inwardly opening U-shaped cross-sectionwhich has an internal radius of curvature R and which has flanges whichhave a length such that the total height of the cross-section is thedimension L. In accordance with one of the features of the presentinvention, these dimensions are formed in the first die 30 such that theradius of the curvature R is substantially greater than the radius ofcurvature R of FIG. 2 and the dimension L, is somewhat longer than thedimension L of FIG. 2. To form a sealing ring 10 having the dimensionsdescribed above, the dimension of the die 30 might be chosen such thatthe radius of curvature R is 0.050 inches and the dimension L, is 0.220inches.

At this point, it is noted that after the tubular ring formed in step 26is cold-rolled in step 28, the thickness of the walls of theintermediate ring shown in FIG. 5 are no longer constantly the same aswas the thickness of the tubular ring prior to the cold rolling. Becausethe tubular ring has now been rolled into a curved crosssection,portions of the wall have been thinned to allow for this curvature. Itis this thinning because of curvature which has led the prior art tobelieve that suitable sealing rings 10 could not be formed by the coldrolling method. However, no account of this thinning is taken at thisfirst cold rolling step 28 of the method, since it will be compensatedfor in. the second cold-rolling step 40 described below.

Returning now to the description of the block flow diagram of FIG. 3,after the intermediate ring shown in FIG. 5 is formed in the step 28,the intermediate ring is subjected to a second cold rolling step 40.This second cold rolling step 40 is performed in the second cold rollingdie 42, which is also shown in FIG. 4.

As is shown in FIG. 4, this second rolling die 42 includes a malerolling member 44 and a female rolling member 46. These elements of thesecond rolling die 42 are dimensions such that, when the male member 44is positioned in the female member 46, a space 48 having the showncross-sectional area is present between these dies. The intermediatering 10 shown in FIG. 5 is placed in the female member 48 and the malemember 44 is rolled into it to cold-roll the intermediate ring into thecross-sectional area of the space 48.

In accordance with one of the primary features of this invention, themale member 44 includes shoulder members 50 which engage the endsurfaces 18 and 20 of the flanges l4 and 16 respectively of the ring 10.

. Thus, when the intermediate ring is cold-rolled the second time in thestep 40, the ring 10 is engaged in the second rolling die 42 both on itsinner and outer surfaces and on the ends of the flanges.

As was noted above in the description of FIG. 5, in thefirst coldrolling step 28, the flanges 14 and 16 were formed longer than weredesired for the finished seal- 2 ing ring. In the second cold rollingstep 40, the end surfaces 18 and 20 of the elongated flanges are engagedby the shoulders 50 on the male die 44, and at least a portion of thisexcess length of the flanges is compressed downwardly into the flangeand caused to cold flow into the curved section 12 of the sealing ring10 to cause the thickness of the sealing ring 10 to increase, eventhough the rolling operation would normally cause the ring to thin, inthe manner described above. Thus, the above described thinning whichmight have occurred in the first cold rolling step 28 is compensatedout, and the desired constant thickness of the sealing ring 10 isprovided. In practice, it has been found that any reasonable desiredthickness of the ring can be provided by adjusting the dimensions of theshoulder 50 and the length of the flanges 14 and 16. It has even beenfound possible to actually increase the thickness of the sealing ring inthe curved portion relative to the thickness of the original tubularring. Thus, in accordance with the present invention, the undesirablethinning which was thought to preclude cold-rolling of such sealingrings is successfully overcome.

FIG. 6 shows a cross-sectional view of the sealing ring 10 after it isremoved from the second die 42 at the conclusion of the second coldrolling step 40. As is shown in FIG. 6, the cross-section of the ring 10now is in the same general shape as is shown in FIG. 2. In the case ofthe typical ring described above, the dimensions are: the internalradius of curvature R of the curved section 12 is now the desired 0.025inches. The length of the flanges l4 and 16 are now such as to form thedimension L shown in FIG. 6. If precise quality control is maintained,this dimension can be cold-rolled to the desired 0.200 inches describedabove. However, it is preferred that the dimension L is still somewhatlonger than this, and might typically be 0.210 inches. The reason forthis is, as is subsequently described below, it is usually desirable tomachine the ring 10 to provide the desired tapering thickness of theflanges l4 and 16 and the desired lands 22 and 24 anyhow, and thisexcess length of the flanges 14 and 16 can then conveniently andeconomically be machined off at the same time to precise dimensions.

Since it is usually desired to heat treat the rings 10 after they havebeen formed into a generally U-shaped inwardly opening cross-section, itis usually desirable that the sealing ring 10 have a smaller outsidediameter than is desired after the second cold rolling step 40 in orderthat it may be stretched or expanded later to precise dimensions.Typically, to form the ring described above, the ring 10 of FIG. 6 mighthave an outside diameter of 3.76 to 3.77 inches.

Returning now to the description of FIG. 3, after the second coldrolling step 40, the next step 42 in the method is to expand the ringprior to heat treating. This ring expansion is conveniently done in anexpanding mandrel of the type well known to those skilled in the art. Inthe case of the ring described above, the ring is first expanded untilit has an outside diameter of 3.785 inches.

After the initial expansion step 42, the next step 44 is to heat treatthe sealing ring 10 in any desired manner to provide the necessary ordesired metallurgical properties to the ring 10. Again, the particulardetails of the heat treating are not given, since they will depend uponthe material from which the ring 10 is formed and the properties whichare desired to be imparted to the ring. The manner .of heat treatingsuch rings is well known to those skilled in the art, and theconventional heat treating methods are used in this invention.

After the heattreating step 44, which can result in some distortion orwarping of the ring 10, the ring is again expanded in the next step 46to the desired final outside dimension. Again, expansion canconveniently occurin the well known expanding mandrels. Since the ringhas now been heat treated and is considerably harder than it was before,it is preferable that as much expansion as possible is done in the firstring expansion step 42 to leave less expansion for the second expansionstep 46.

After the second expansion step 46, and preferably while the ring 10 isstill being supported by the expanding mandrel, the final step 48 in themethod is to machine the ring 10 to the desired final dimensions. Atthis time, the desired taper in the flanges 14 and 16 can be machinedinto the ring, the lands 22 and 24 can be formed and the end surfaces 18and 20 of the flanges can be cut to the desired final length.

By the method just described, sealing rings are formed in a simple andeconomical manner. In addition, the sealing rings which are formed bythis method are actually superior to the prior art sealing rings formedby other methods. As was noted above, since the sealing ring 10 isformed from an originally flat strip of metal, rather than beingmachined from a solid piece of metal, the grain structure in the ring isconstant relative to the cross-section all the way around the ring. Inaddition, the cold flow of metal downward into the ring in the secondcold rolling step 40 above moves the neutral axis of the ring outward,and thereby renders the ring less likely to fracture when it is in use.Yet another advantage is that, since the rings go through two expansionsteps, the expansion steps 42 and 46 described above, the quality of theweld which formed the tubular ring in the step 26 is inherently tested,and only those rings which have a suitable high quality weld can besuccessfully expanded. Those rings which have weak welds will ruptureduring the expansion steps, and thus it is assured that only highquality rings will complete the operation. This is an especiallyadvantageous feature, since the weld is a common place for such rings tofail.

While the invention is thus disclosed and the presently preferredembodiment described in detail, it is not intended that the invention islimited to these shown embodiments. Instead, many modifications willoccur to those skilled in the art which lie within the spirit of theinvention. It is thus intended that the invention be limited in scopeonly by the appended claims.

What is claimed is: 1. The method of manufacturing a sealing ring or thelike having predetermined outside and inside diameters and a generallyU-shaped inwardly opening cross section, said cross-section having apredetermined internal radius of curvature and flanges of a predeter'mined flange length, said method comprising the steps of:

forming a tubular band of metal whose diameter is between saidpredetermined outside and inside diameters,

rolling said tubular band int0 an intermediate ring in a first die untilit hasa generally U-shaped inwardly opening cross-section having aninternal radius of curvature greater than said predetermined internalradius and having flanges longer than said predetermined flange length,and

rolling said intermediate ring in a second die until said ring has saidpredetermined internal radius of curvature, said second die engaging theinner surface, the outer surface and the ends of the flanges of saidring to force metal to cold flow from said flanges down into the curvedportion of the crosssection to prevent thinning of said curved portionof said ring. 7

2. The method of claim 1 in which said sealing ring is formed to have anoutside diameter less than said predetermined outside diameter aftersaid second rolling step and which further comprises the step ofstretching said ring after said second rolling step until said ring hassaid predetermined outside diameter.

3. The method of claim 2 which further comprises the step of heattreating said sealing ring prior to said step of stretching said ring.

4. The method of claim 3 which further comprises the step of initiallystretching said ring prior to said step of heat treating said ring.

5. The method of claim 1 which further comprises the step of machiningsaid ring to predetermined dimensions after said second rolling step.

1. The method of manufacturing a sealing ring or the like havingpredetermined outside and inside diameters and a generally Ushapedinwardly opening cross-section, said cross-section having apredetermined internal radius of curvature and flanges of apredetermined flange length, said method comprising the steps of:forming a tubular band of metal whose diameter is between saidpredetermined outside and inside diameters, rolling said tubular bandint0 an intermediate ring in a first die until it has a generallyU-shaped inwardly opening crosssection having an internal radius ofcurvature greater than said predetermined internal radius and havingflanges longer than said predetermined flange length, and rolling saidintermediate ring in a second die until said ring has said predeterminedinternal radius of curvature, said second die engaging the innersurface, the outer surface and the ends of the flanges of said ring toforce metal to cold flow from said flanges down into the curved portionof the cross-section to prevent thinning of said curved portion of saidring.
 2. The method of claim 1 in which said sealing ring is formed tohave an outside diameter less than said predetermined outside diameterafter said second rolling step and which further comprises the step ofstretching said ring after said second rolling step until said ring hassaid predetermined outside diameter.
 3. The method of claim 2 whichfurther comprises the step of heat treating said sealing ring prior tosaid step of stretching said ring.
 4. The method of claim 3 whichfurther comprises the step of initially stretching said ring prior tosaid step of heat treating said ring.
 5. The method of claim 1 whichfurther comprises the step of machining said ring to predetermineddimensions after said second rolling step.